The “Duck-billed” Dinosaur That Wasn’t

Instead of a long, low duck bill, the beak of Tethyshadros was shaped like a snowplow and serrated. Why it had such a strange beak is a mystery

A restoration of the island hadrosauroid Tethyshadros by Nobu Tamura. Image from Wikipedia.

Everyone knows what a “duck-billed” dinosaur was. This bit of shorthand has been permanently grafted onto the hadrosaurs—the widespread group of herbivorous dinosaurs with elongated skulls and what appear to be duck-like beaks.

The title made perfect sense during the early 20th century when these dinosaurs, such as Edmontosaurus and Parasaurolophus, were thought to be amphibious creatures that dabbled in the water for soft plants and escaped into Cretaceous lakes when predators came near. If the dinosaurs looked like monstrous ducks, then they must have acted like ducks. But that vision of paddling hadrosaurs was discarded decades ago. These dinosaurs were terrestrial animals, and discoveries of well-preserved hadrosaur beaks have indicated that the mouths of these dinosaurs were not so duck-like, after all. One beautifully preserved Edmontosaurus skull on display at the Natural History Museum of Los Angeles shows that the tough beak of this dinosaur ended in squared-off, almost vertical croppers and not a duck-like, spoon-shaped bill. The so-called duck-billed dinosaurs didn’t look like mallards at all. And one of the strangest variations in beak shape was found in a small, island-dwelling hadrosauroid described in 2009.

On the basis of a nearly complete and articulated skeleton, paleontologist Fabio Dalla Vecchia named the dinosaur Tethyshadros insularis. The name is a testament to where the dinosaur lived. During the time of Tethyshadros, around 71 million years ago, an ancient sea called Tethys covered most of southern Europe. This oceanic incursion created chains of islands, and it was on one of these islands—where Italy sits today—that Tethyshadros lived. More than that, the isolation of the dinosaur on the island might have been responsible for the dinosaur’s relatively small size (about 13 feet long) compared to its distant, North American cousins such as Edmontosaurus—it’s an example of a phenomenon called insular dwarfism that has been documented for other prehistoric herbivores, including dinosaurs.

But one of the most peculiar aspects of Tethyshadros was its beak. Instead of a long, low duck bill, the upper beak of this dinosaur was a ridged structure jutting out in a shape roughly reminiscent of a snowplow. And rather than being smooth, the margin of the upper beak was pointed, with the middle point being the largest. This general type of serrated beak has been seen before in iguanodontian dinosaurs—the stock from which hadrosaurs evolved, with Tethyshadros being closer to hadrosaurs than to the iguanodontians—but never before in such an extreme shape. Why Tethyshadros had such a strange beak is a mystery. As paleontologist Darren Naish wrote in his detailed summary of this new dinosaur, “Did help Tethyshadros to bite at specific food items? Were they for grooming? For display? The mind boggles.”

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